The present invention relates to improvements in methods of dispensing soap and to improvements in soap dispensing apparatus.
It is known to install manually operable dispensers for liquid soap in public lavatories and like establishments. As a rule, a dispenser for liquid soap is equipped with a pivotable lever whose manipulation results in dispensing of a certain quantity of liquid soap into the palm or onto the back of a hand which must be placed beneath the outlet of a spout for evacuation of liquid soap. A drawback of such dispensers for liquid soap is that droplets of liquid soap are frequently discharged by the spout after the lever is released and after the hand which collects the major part of the quantity of dispensed liquid soap is already removed from a receiving position beneath the spout. The droplets of liquid soap gather in a sink or on the floor and must be collected from time to time in order to enhance the appearance of the lavatory and/or to avoid the likelihood of injury to persons using such facilities. Dispensers of the above outlined character are often installed in rest rooms including those in schools, restaurants, airline terminals, government buildings, office buildings and many others.
In order to eliminate the problems which arise as a result of dripping of liquid soap from liquid soap dispensers, it was already proposed to dispense batches of soap lather, i.e., a mixture of liquid soap and bubbles of air. Reference may be had, for example, to European Pat. No. 0 019 582 which discloses a dispenser embodying a lather generator wherein liquid soap and air are converted into soap lather and which discharges a batch of lather in response to pivoting of a lever. The dispenser of the European patent comprises a vessel for liquid soap and a lather generator defining a cylindrical space which receives liquid soap from the vessel. A metering pump which employs a reciprocable piston is provided to expel liquid soap from the cylindrical space into a mixing chamber. The latter is connected with a diaphragm pump which can be actuated by a lever simultaneously with the metering pump. When the lever is pivoted by a person who desires to wash her or his hands, the lever causes the metering pump to expel liquid soap from the cylindrical space into the mixing chamber (the cylindrical space was filled with liquid soap). Such liquid soap cannot return into the cylindrical space because the patented dispenser employs a check valve which prevents the flow of liquid soap from the metering chamber back into the cylindrical space. A restoring spring thereupon automatically pivots the lever back to its starting position which, in turn, causes the diaphragm pump to force air into the mixing chamber whereby the admitted air forms large bubbles and the contents of the mixing chamber are converted into a mixture of air and liquid soap. The mixture is expelled from the mixing chamber through a porous partition and into an expansion chamber, and the resulting fine lather (containing small bubbles of air) is discharged into or onto the hands of the person awaiting the issuance of a batch of lather.
A drawback of the patented dispenser for soap lather is that the consistency of lather varies within a rather wide range. This is believed to be attributable to the fact that the conditions for the making of lather vary with time, primarily because liquid soap must be conveyed through and tends to deposit in narrow conduits and the initially obtained mixture of air and liquid soap must pass through a porous partition which becomes clogged as a result of repeated use. This entails pronounced changes of pressure and equally pronounced changes of the ratio of liquid soap to air in the mixing chamber as well as in the expansion chamber of the patented lather dispenser. The only presently known solution to overcome the problems in connection with the utilization of the patented lather dispenser is to resort to frequent cleaning which contributes significantly to maintenance cost and renders the patented dispenser less desirable for many applications. Moreover, the patented dispenser is expensive because it must be equipped with different types of pumps and cannot guarantee complete expulsion of a freshly gathered batch of lather from the expansion chamber.